The new rule, published Feb. 29 in the Federal Register, matches OSHA protections already in place for almost all other workers.
"This final rule will help improve health protection for miners who work in an environment where asbestos is present," said MSHA Administrator Richard Stickler. "Furthermore, it will help lower the risk of material impairment of health or functional capacity over a miner's working lifetime."
The rule lowers MSHA's permissible exposure limit (PEL) for asbestos from two fibers per cubic centimeter to 0.1 fibers. It also lowers the allowable limit for brief exposures to higher asbestos levels from 10 fibers per cubic centimeter for 15 minutes to one fiber for 30 minutes.
MSHA will retain its existing method for analyzing asbestos samples (phase-contrast microscopy) and the existing counting criteria (particles 5 micrometers or longer with a length to diameter ratio of at least 3 to 1). Additionally, MSHA will continue to use transmission electron microscopy to confirm samples that exceed the new PEL.
Asbestos exposure is linked to lung cancer, mesothelioma and other cancers, as well as asbestosis and other nonmalignant respiratory diseases. But for years, MSHA's permissible exposure limit allowed miners to be exposed to 20 times more asbestos than workers covered by OSHA's rules.
A report released by the Department of Labor's Inspector General (IG) urged MSHA to change the rule after miners and their families began dying of asbestos exposure in the town of Libby, Mont. MSHA began rulemaking a year after the IG report and published the proposed asbestos exposure limit rule in July 2005.
There are no operating asbestos mines in the United States, but a few operating mines currently have asbestos in the ore, MSHA said. The agency's sampling data show that five metal and nonmetal mines – 2 percent of the 207 mines sampled since 2000 – have recorded asbestos exposure over the final rule's limit.